The coaxial compound helicopter (CCH) system has characteristics such as strong non-linearity, significant coupling, diverse flight modes, as well as control redundancy in the transition mode. This paper proposes a variable-bandwidth extended state observer–based improved active disturbance rejection control (VBADRC) scheme for full-envelope flight control of the CCH. This scheme primarily addresses the influences of disturbances, unmodeled dynamics and parameter uncertainties on the system. A variable-bandwidth extended state observer (VBESO) is proposed to handle the internal unmodeled dynamics and external disturbances of CCH, effectively improving the disturbance-estimation accuracy and mitigating the initial peak phenomenon. To suppress the effects of parameter deviations on the controller in different modes, an adaptive feedback controller incorporating an online adaptive mechanism is proposed to achieve real-time parameter adjustment and disturbance compensation. Furthermore, to manage the control allocation problem during transition flight, a weighted pseudoinverse-based multistage allocation strategy is designed to handle the constantly changing control authorities. The performance of the presented scheme is validated through simulation, demonstrating strong robustness and excellent tracking capability even in the case of external disturbances and internal uncertainties.
This paper investigates the output regulation problem using an observer-based inverse optimal controller within the nonlinear servomechanism framework for asymptotic convergence to desired references and rejection of time-varying disturbances generated by an exosystem. To address the practical constraint of full-state measurements, the system’s internal and external state estimation is done via a full-order high-gain observer. These estimated states are incorporated into the inverse optimal controller augmented with a conditional servocompensator within the Lyapunov redesign and saturated high-gain feedback framework to enhance transient performance and achieve asymptotic steady-state regulation. The proposed control scheme combines the optimality and robustness properties offered by the state feedback controller with disturbance rejection and state estimation in an output-feedback framework. The proposed output-feedback controller is validated on a nonlinear DC motor using MATLAB/Simulink. Finally, comparative simulations against baseline controllers further exhibit the robustness, performance, and practical feasibility of the proposed controller for high-performance control tasks.
The controller for point-to-point (PTP) servo motion control is required to exhibit a high dynamic response, minimal position-tracking error, and robust disturbance rejection capabilities. Conventional cascaded position–velocity–current architectures often fall short in PTP applications due to the delay introduced by the velocity loop. To address this issue, a dual-loop position controller is proposed, consisting of an outer position loop and an inner current loop. This controller integrates a disturbance torque observer that leverages position signal measurements to enhance robustness. The observer employs a first-order low-pass filter to mitigate noise and measurement errors in the current and position feedback signals. This control architecture is designed to be straightforward and easy to implement. To enhance the transient response to sudden load disturbances, an acceleration-feedback mechanism is integrated into the observer path to bolster disturbance compensation. Experimental results have demonstrated the efficacy of the proposed scheme. In comparison to conventional dual-loop position–current servos, the proposed approach enhances dynamic performance without compromising response time or position tracking performance.
Active disturbance rejection control (ADRC) is a powerful control method for complex systems, demonstrating exceptional robustness against uncertainties and disturbances. Nevertheless, its observer-based framework exhibits inherent sensitivity to measurement noise, which may lead to amplified high-frequency noise components in the control signal. In view of this, this article develops a noise-reduction filter-assisted active disturbance rejection controller (NRFADRC), ensuring high-accuracy attitude tracking control. Firstly, NRFADRC utilizes a novel continuously differentiable function with saturation constraints to design the nonlinear feedback controller and the extended state observer (ESO), mitigating chattering phenomena near switching points. Subsequently, a noise-reduction filter with phase-leading compensation is deployed upstream of ESO, improving the ESO’s state and disturbance estimation accuracy under noisy conditions. Moreover, an innovative Harris hawk optimization algorithm with balanced exploration-exploitation dynamics is developed to optimize the controller parameters. Herein, EHHO introduces the elite guidance-based exploration strategy, the population diversity-based adaptive transition mechanism, and the dynamic Levy flight-based exploitation strategy. Eventually, NRFADRC-based pitch attitude controller is designed, and extensive numerical simulations are conducted. The results demonstrate that the NRFADRC-based controller can realize robust and stable control performance even with control input noise, sensor measurement noise, and atmospheric turbulence.